The present invention relates generally to a system for supplying a flush fluid to a semiconductor polishing machine or other apparatus. More particularly, the invention relates to a system for flowing de-ionized (DI) water through an apparatus to prevent slurry from clogging the apparatus and/or to prevent malfunctioning of valves or pumps. The present invention also relates to a control system for operating a flush system.
In the course of manufacturing integrated circuits, it is typically desirable to selectively polish or planarize the surfaces of semiconductor wafers. Such mechanical treatment may be done to remove high topography, surface defects, scratches, roughness, or embedded particles. A chemical slurry may be used during such polishing to facilitate high removal rates and film selectivity. Polishing with slurry is sometimes called chemical-mechanical planarization (CMP).
Known CMP systems are illustrated in U.S. Pat. No. 5,679,169 (Gonzales et al.), U.S. Pat. No. 5,679,065 (Henderson), U.S. Pat. No. 5,658,183 (Sandhu et al.), U.S. Pat. No. 5,645,682 (Skrovan), U.S. Pat. No. 5,643,060 (Sandhu et al.), U.S. Pat. No. 5,514,245 (Doan et al.), and U.S. Pat. No. 5,314,843 (Yu et al.).
Slurries for use in CMP tools may contain small, abrasive particles and/or reactive chemicals. Conventional CMP slurries contain solutions of alumina or silica. Other slurries for integrated circuit (IC) manufacturing processes are mentioned in U.S. Pat. No. 5,664,990 (Adams et al.). Slurries tend to dry out, especially when they become stagnant or are exposed to air. Slurries may clog the conduits in polishing machinery and other manufacturing apparatuses. In addition, slurries can cause valves and pumps to stick or malfunction.
The present invention relates to a system for conveniently and reliably flushing slurry equipment with DI water (or another suitable flush fluid). In one aspect of the invention, a one-way check valve is used to supply the DI water to the slurry equipment at a controlled pressure.
In another aspect of the invention, a second check valve is used as a pressure regulator to control the pressure of the DI water upstream from the first check valve. In a preferred embodiment of the invention, the second check valve operates by draining relatively high pressure DI water away from the first check valve.
In another aspect of the invention, one-way valves are employed to provide a precisely controlled source of low pressure DI water.
The present invention also relates to a system that supplies slurry to a CMP tool at a pressure greater than the pressure of the flush liquid. This way, the flush liquid does not enter the slurry distribution conduits even when the valves in the system malfunction.
The present invention provides an uncomplicated, dependable and economical system for supplying flush liquid to clean an apparatus that uses slurry. In a preferred embodiment of the invention, the system employs spring-loaded one-way valves to control the pressure and flow direction of the flush liquid. In another aspect of the invention, a four-port valve apparatus (with two inlets and two outlets) is employed to control the flow of slurry.
The present invention may be adapted for use with a Strasbaugh 6DS-SP wafer polishing system. However, the invention should not be limited to any particular machinery. The invention is applicable to a variety of wafer handling systems. In addition, the invention may be used to flush materials other than slurry. For example, the invention may be used to flush caustic soda from a fluid handling apparatus. In addition, the invention may use dry air or nitrogen as a flush fluid. The invention is not limited to use with CMP or other slurry handling equipment.
In a preferred embodiment of the invention, a programmable system provides automatic and manual flush sequence control. The operation of the system may be. programmed for predetermined delays and periodic timed flush cycles.
An advantage of the invention is that it can prevent contamination of slurry by DI water even in the event of a system malfunction. Another advantage is that the invention may be used to prevent slurry from flowing into the source of the DI water.
Another advantage of the invention is that it avoids the need for a conventional high purity pressure regulator. Such conventional high purity pressure regulators are generally expensive and tend to not regulate well. Thus, the invention may be employed at relatively low cost and in an uncomplicated manner.
These and other features and advantages of the invention will become apparent from the following detailed description of preferred embodiments of the present invention.